A great many types of devices for absorbing the impact effect of kinetic energy are heretofore known for use in automobile safety seat belts. Most promising is use in such belts of devices whose action is based on plastic deformation of some textile materials, which is accounted for by their simple construction, high reliability and low cost. However, effective application of textile shock absorbers may be hampered for some types of devices by difficulties involved in providing a high operating threshold, and for other types, by considerable loss of strength occurring in the case of high-rate loading due to heat evolution resulting from interaction of structural elements of a textile material. That is why the provision of devices for effective damping of high-rate loading is an urgent problem nowadays.
Known in the present state of the art is a construction of a damping device for an automobile safety seat belt. The device consists of a textile band folded into a loop and stitched across with sewing threads. The thus-stitched loop is pressed against one of the textile band ends and a sleeve is fitted onto the loop and the band end. Then one of the band ends is attached to the car body, the other being held to the band of the safety seat belt. Once the load imposed upon the safety seat belt has exceeded the operating threshold of the damping device it starts absorbing energy. As a result, first the sleeve is liable to destruct, then the sewing thread stitches do so in succession.
It is however too difficult to make packaged damping devices featuring the operating threshold of 1000 kgf and over using the now-adopted technique for joining the textile band of the device. Practice demonstrates that, when using textile bands 30 to 40 mm wide made from yarn having a tensile breaking strength of 65 to 70 gf/tex, it is difficult to produce damping devices having the operating threshold in excess of 200 kgf. In addition, the operating threshold of the device is liable to considerably reduce at a fast-rate loading as compared to the results of static loading. It is also impossible to carry out a reliable nondestructive check for quality of the sewing joint, which affects adversely its reliability.
One more device for damping the impact load in a safety system is known in the art, comprising a support and a flexible untearable band associated with said device, said band incorporating an energy-absorbing means liable to destruct under the load applied. The energy-absorbing device is made as a strap built up of two bands bonded together. One end of the flexible untearable band is associated with the car body, while the other, with the bracket likewise fastened on the car body. The bracket carries also a reel for one of the ends of the safety seat belt band to hold and wind up. In the case of an abrupt loading of the safety seat belt the reel, provided with special retainers, wedges up the band, thus preventing it from unreeling. Once a preset load is attained the bracket along with the reel is detached from the car body, whereupon the strap of the flexible band of the device for damping impact load starts taking up load. As a result, the strap begins separating into two portions at a preset load and thus absorbing surplus kinetic energy.
However, the known damping discussed hereinbefore likewise offers no possibility of carrying out a nondestructive reliable check for quality of bonded joints, especially after operation under different atmospheric conditions, which affects adversely the reliability of the device.